同类和异类 AA6082 和 AA7075 摩擦搅拌焊接坯料的高应变速率拉伸变形

IF 3.8 Q2 MATERIALS SCIENCE, MULTIDISCIPLINARY
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引用次数: 0

摘要

在过去十年中,摩擦搅拌焊接工艺克服了凝固裂纹、相位偏析和表面氧化等基本焊接难题,已成为连接异种轻质材料的成熟固态技术。尽管具有这些独特的功能,但焊接区所产生的微观结构特征由具有高位错密度的细晶粒组成,这对进一步的热处理和成型工艺提出了挑战。因此,较高的固溶退火温度会导致调整后的微观结构退化,并降低沉淀硬化铝合金异种接头的机械性能。因此,后续的热成型工作非常繁重,需要进一步的热处理步骤。因此,本研究调查了最近引入的新型热机械成型工艺对薄壁 AA6082 和 AA7075 毛坯通过摩擦搅拌焊接技术加工的相似和不相似接头的局部变形行为的影响。为了避免完全消除调整后的微观结构,焊接过程是在由固溶退火、模具冷却和峰值时效组成的热机械过程之后进行的。然后在 ε˙ = 40 s-1 到 ε˙ = 400 s-1 的高应变速率下进行单轴拉伸试验。结果表明,随着应变速率的增加,屈服强度和极限拉伸强度以及破坏后的总伸长率都有所增加。随着应变速率的增加,AA7075 类似焊缝的流动应力高于 AA6082 以及 AA6082 和 AA7075 异种焊缝。局部变形测量结果表明,类似焊缝的焊接区应变局部化程度较高,这会导致微裂纹的产生,并因应变累积而失效。显微结构分析表明,搅拌摩擦焊接过程后,金块区的晶粒结构非常精细,析出物分布均匀,这解释了塑性变形行为。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
High strain rate tensile deformation of similar and dissimilar AA6082 and AA7075 friction-stir-welded blanks
Friction-stir-welding process has become an established solid-state technique for joining of dissimilar lightweight materials over the past decade by overcoming fundamental welding challenges such as solidification cracking, phase segregation and surface oxidation. Despite these unique capabilities, the resulting microstructure feature in the weld zone consisting of fine grains with a high dislocation density, challenges further heat treatment and forming processes. Hence, a high solution annealing temperature results in degradation of the adjusted microstructure and in a lower to reduced mechanical properties in case of dissimilar joints of precipitation-hardenable aluminum alloys. Subsequent hot forming therefore involves a great effort and requires further heat treatment steps. Thus, the present study investigates the effect of a recently introduced novel thermo-mechanical forming process on local deformation behavior of similar as well as dissimilar joints processed by friction-stir-welding technique of thin-walled AA6082 and AA7075 blanks. To avoid the complete elimination of the adjusted microstructure, the welding process is performed after a thermo-mechanical process consisting of solution annealing, die cooling and peak aging. Uniaxial tensile tests are then carried out at high strain rates ranging from ε˙ = 40 s-1 to ε˙ = 400 s-1. The results show an increase in yield and ultimate tensile strength as well as in total elongation after failure with increasing strain rates. As the strain rate increases, the flow stress of similar weld of AA7075 is higher than those of AA6082 and the dissimilar weld of AA6082 and AA7075. Local deformation measurements reveal higher strain localization in the welded zone for similar welds, which leads to micro-crack initiation and failure due to strain accumulation. Microstructure analysis shows very fine equiaxed grain structure in the nugget zone and homogenous distribution of precipitates after friction stir welding process, which explain the plastic deformation behavior.
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来源期刊
CiteScore
7.10
自引率
9.80%
发文量
58
审稿时长
44 days
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